VOF with evaporation and condensation UDF's

gerardosrez · February 13, 2015, 20:57

Hello colleagues,

I have a question for those who know Fluent from its inside...

The VOF model theory states that only mass conservation equation is solved for secondary phases, therefore they called them the volume fraction conservation equations....At the end the primary phase volume fraction is the unity less the sum of secondary phases mass fractions....

So if I implement UDF to model evaporation and condensation (for example: water) mass sources, why should I have to write UDF for both cond/evap mass sources for primary phase if it is going to be calculated after volume fractions of secondary phases are done...

Best regards...

ndabir · February 16, 2015, 12:07

Can't you just use the evaporation-condensation option for mass transfer in the phase interaction toolbar instead of using a UDF?

When I use VOF, the evaporation-condensation option for mass transfer is available and can be used. I use Ansys Fluent 13. Maybe this option is not available in other versions of the software.

kbaker · February 20, 2015, 03:22

Hello guys I have a question : is the evaporation-condensation option work properly with VOF model?

gerardosrez · March 14, 2015, 19:37

Dear colleagues thanks for your answers....

I found this in the User's Guide...

evaporation-condensationenables you to apply the evaporation-condensation model as the mass transfer mechanism. This model is available with the mixture and Eulerian multiphase models. Refer to Evaporation-Condensation Model in the Theory Guide for a theoretical discussion about this model.

According to this the evaporation-condensation model is not available to be used with VOF simulations...I know you can select it from the User Inteface but it seems that it does not work....

Even if this is available or not, I'd like to consult the main question of my post which is what happens with the mass source calculated, by a UDF, for primary phases if no vof equation is solved for this one...

Best regards...and again thanks for your answers....

kbaker · March 15, 2015, 15:01

Dear gerardosrez thanks for illustration. About your question if you not use vof model so what model of multiphase flow you tried? furthermore selecting which of the phases be primary or secondary that is your choice and you can set any of the phases as primary or secondary as you like? I think your question seems obvious something?

kbaker

February 13, 2015, 20:57	VOF with evaporation and condensation UDF's	#1
gerardosrez Member G. S. Join Date: Nov 2010 Posts: 54 Rep Power: 15	Hello colleagues, I have a question for those who know Fluent from its inside... The VOF model theory states that only mass conservation equation is solved for secondary phases, therefore they called them the volume fraction conservation equations....At the end the primary phase volume fraction is the unity less the sum of secondary phases mass fractions.... So if I implement UDF to model evaporation and condensation (for example: water) mass sources, why should I have to write UDF for both cond/evap mass sources for primary phase if it is going to be calculated after volume fractions of secondary phases are done... Best regards...

March 14, 2015, 19:37		#4
gerardosrez Member G. S. Join Date: Nov 2010 Posts: 54 Rep Power: 15	Dear colleagues thanks for your answers.... I found this in the User's Guide... evaporation-condensationenables you to apply the evaporation-condensation model as the mass transfer mechanism. This model is available with the mixture and Eulerian multiphase models. Refer to Evaporation-Condensation Model in the Theory Guide for a theoretical discussion about this model. According to this the evaporation-condensation model is not available to be used with VOF simulations...I know you can select it from the User Inteface but it seems that it does not work.... Even if this is available or not, I'd like to consult the main question of my post which is what happens with the mass source calculated, by a UDF, for primary phases if no vof equation is solved for this one... Best regards...and again thanks for your answers....

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February 16, 2015, 12:07		#2
ndabir Senior Member navid Join Date: Jan 2010 Posts: 110 Rep Power: 16	Can't you just use the evaporation-condensation option for mass transfer in the phase interaction toolbar instead of using a UDF? When I use VOF, the evaporation-condensation option for mass transfer is available and can be used. I use Ansys Fluent 13. Maybe this option is not available in other versions of the software.

February 20, 2015, 03:22		#3
kbaker Senior Member Khalid Baker Join Date: Mar 2009 Location: IRAQ Posts: 168 Rep Power: 17	Hello guys I have a question : is the evaporation-condensation option work properly with VOF model?

March 15, 2015, 15:01		#5
kbaker Senior Member Khalid Baker Join Date: Mar 2009 Location: IRAQ Posts: 168 Rep Power: 17	Dear gerardosrez thanks for illustration. About your question if you not use vof model so what model of multiphase flow you tried? furthermore selecting which of the phases be primary or secondary that is your choice and you can set any of the phases as primary or secondary as you like? I think your question seems obvious something? kbaker